THE SMALL INTESTINE. 



919 



Capillary network. 



mouth. They are believed by Watney to be direct continnations of the pyloric 

 Clauds of the stomach. They consist of a number of tubular alveoli, lined by 

 epithelium, and opening by a single duct on the inner surface of the intestine. 



The solitary glands (glandulce solitaries) are found scattered throughout the 

 mucous membrane of the small intestine, but are most numerous in the lower part 

 of the ileum. They are small, round, whitish bodies, from half a line to a line in 

 diameter. Their free surface is covered with villi, and each gland is surrounded 

 by the openings of the follicles of Lieberkuhn. They are now recognized as 

 lymph-follicles, and consist of a dense 

 interlacing retiform tissue closely packed 

 with lymph-corpuscles, and permeated 

 with an abundant capillary network (Fig. 

 501). 'The interspaces of the retiform 

 tissue are continuous with larger lymph- 

 spaces at the base of the gland, through 

 which they communicate with the lacteal 

 system. They are situated partly in the 

 submucous tissue, partly in the mucous 

 membrane, whence they form slight pro- 

 jections of its epithelial layer, after having 

 penetrated the muscularis mucosae. The 

 villi which are situated on them are 

 generally absent from the very summit 

 (or "cupola," as Frey calls it) of the 

 gland. 



Peyer's glands (agminated glands) 

 (Figs. 501 to 504) may be regarded as 

 aggregations of solitary glands, forming 

 circular or oval patches from twenty to 

 thirty in number, and varying in length 

 from half an inch to four inches. They 

 are largest and most numerous in the 

 ileum. In the lower part of the jejunum they are small, of a circular form, and 

 few in number. They are occasionally seen in the duodenum. They are placed 

 lengthwise in the intestine, and are situated in the portion of the tube most 



FIG. 501. Transverse section through the equa- 

 torial plane of three of I'eyer's follicles from the 

 rabbit. 



FIG. 5Q2. Patch of Peyer's glands. 

 From the lower part of the ileum. 



FIG. 503. A portion of the above 

 magnified. 



distant from the attachment of the mesentery. Each patch is formed of a group 

 of the above-described solitary glands covered with mucous membrane, and in 

 almost every respect are similar in structure to them. They do not, however, as 



